Brushes of DC machine are made up of ?

166 views

Brushes of DC machine are made up of ?

by

1 Answer

Answer :

Brushes of DC machine are made up of carbon.

Like 1 like
by

Please log in or register to answer this question.

Related questions

99 views
In a DC motor, it is important to place the brushes along ______

Description : In a DC motor, it is important to place the brushes along ______ A) Magnetic Neutral Axis B) Normal Geometric Axis C) Nominal Geometric Axis D) None of these

Last Answer : In a DC motor, it is important to place the brushes along Magnetic Neutral Axis

1 answer
121 views
From which material field coils of DC generator are made of?

Description : From which material field coils of DC generator are made of?

Last Answer : Field coils of DC generator are usually made of copper.

1 answer
89 views
Brushes of D.C. machines are made of?

Last Answer : Brushes of D.C. machines are made of carbon.

1 answer
130 views
A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2

Description : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

Last Answer : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87

1 answer
604 views
A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and

Description : A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively

Last Answer : A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively 19,17

1 answer
384 views
The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors

Description : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is  (1) 1000V (2) 100V (3) 600V (4) 10,000V

Last Answer : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V

1 answer
625 views
Aluminium is not used as winding wire for the armature of a dc machine because

Description : Aluminium is not used as winding wire for the armature of a dc machine because  (1) aluminium has low resistivity (2) a large winding space is taken by aluminium conductors and creates ... ) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

Last Answer : Aluminium is not used as winding wire for the armature of a dc machine because  (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

1 answer
185 views
In a dc machine, interpoles are used to

Description : In a dc machine, interpoles are used to  (1) neutralize the effect of armature reaction in the interpolar region (2) generate more induced emf in the armature (3) avoid interference of the armature flux with the main -field flux (4) reduce the demagnetizing effect of armature reaction

Last Answer : In a dc machine, interpoles are used to neutralize the effect of armature reaction in the interpolar region

1 answer
124 views
Why poles of dc machine are laminated?

Description : Why poles of dc machine are laminated?

Last Answer : Poles of DC machines are laminated to reduce the eddy current losses in the poles.

1 answer
174 views
Losses in dc machine..?

Last Answer : Copper losses,iron losses,variable losses , constant losees

1 answer
194 views
Explain concept of back emf in DC machine. State how it governs armature current.

Description : Explain concept of back emf in DC machine. State how it governs armature current. 

Last Answer : Back emf: When the armature of DC machine rotates under the influence of driving torque, the armature conductors move in the magnetic field and cut it and hence emf is induced in them. The ... flow of armature current i.e. it automatically changes the armature current to meet load requirements.

1 answer
169 views
The magnetic neutral plane shifts in a dc machine

Description : The magnetic neutral plane shifts in a dc machine (A) in the direction of motion of motor (B) in the direction of motion of generator (C) due to increase in the field flux (D) cause reduction of flash over between commutator segments

Last Answer : The magnetic neutral plane shifts in a dc machine in the direction of motion of generator

1 answer
122 views
What is the percentage of stray losses in DC machine?

Description : What is the percentage of stray losses in DC machine?

Last Answer : Percentage of stray losses in DC machine is about 1 % .

1 answer
121 views
what are the losses in DC machine?

Last Answer : Iron loss, copper loss and mechanical losses these are the losses in DC machine.

1 answer
120 views
Copper brushes in D.C. machine are used?

Last Answer : Copper brushes in D.C. machine are used where low voltage and high currents are involved.

1 answer
228 views
In a D.C. machine stray loss is the sum of?

Last Answer : In a D.C. machine stray loss is the sum of iron loss and mechanical loss.

1 answer
3.0k views
To avoid formation of grooves in the commutator of a D.C. machine?

Last Answer : To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.

1 answer
163 views
Open circuited armature coil of a D.C. machine is?

Last Answer : Open circuited armature coil of a D.C. machine is identified by the scarring of the commutator segment to which open circuited coil is connected and indicated by a spark completely around the commutator.

1 answer
673 views
In case of D.C. machine winding, number of commutator segments is equal to?

Last Answer : In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.

1 answer
164 views
Iron losses in a D.C. machine are independent of variations in?

Last Answer : Iron losses in a D.C. machine are independent of variations in load.

1 answer
86 views
In a four-pole D.C. machine?

Last Answer : In a four-pole D.C. machine alternate poles are north and south.

1 answer
82 views
The rapid wear of brushes takes place due to?

Last Answer : The rapid wear of brushes takes place due to abrasion from dust, excessive spring pressure, rough commutator bars, high mica insulation between com-mutation bars.

1 answer
199 views
Armature coil is short circuited by brushes when it lies?

Last Answer : Armature coil is short circuited by brushes when it lies along neutral axis.

1 answer
162 views
The number of brushes in a commutator depends on?

Last Answer : The number of brushes in a commutator depends on amount of current to be collected.

1 answer
154 views
The material for commutator brushes is generally?

Last Answer : The material for commutator brushes is generally carbon.

1 answer
327 views
In lap winding, the number of brushes is always?

Last Answer : In lap winding, the number of brushes is always same as the number of poles.

1 answer
61 views
The rotor of a hysteresis motor is made of?

Last Answer : The rotor of a hysteresis motor is made of chrome steel.

1 answer
230 views
UNIT 1 fundamentals of AC rotating machine

Description : UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor ( ... alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization

Last Answer : 1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.

2 answers
173 views
The measured torque and torque reference of an induction machine are shown in Fig. 2.

Description :  Analyze the differences of FOC and DTC. The switching frequency of FOC is 1.3 kHz and the average switching frequency of DTC is the same.

0 answers
622 views
In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation,

Description : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as  (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator

Last Answer : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator 

1 answer
203 views
The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)

Description : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)  (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

Last Answer : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

1 answer
132 views
Torque angle for the synchronous machine is the angle between

Description : Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop

Last Answer : Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap

1 answer
273 views
In DC generators lamination core are generally made of?

Description : In DC generators lamination core are generally made of?

Last Answer : In DC generators lamination core are generally made of silicon steel.

1 answer
258 views
Draw the stator voltage curves during the four different start-up methods shown in figure

Description : I got some grapic drawing questions guys and I need to see the answers immediately.Stator voltage curve for each four different start up methods.

0 answers
146 views
Describe the reason of using dc series motor for electric trains.

Description : Describe the reason of using dc series motor for electric trains.

Last Answer : Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains

1 answer
498 views
A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s.

Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Last Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

1 answer
358 views
A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance

Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

Last Answer : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

1 answer
410 views
The fall in speed of a dc generator due to increase in load can be corrected by

Description : The fall in speed of a dc generator due to increase in load can be corrected by  (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover

Last Answer : It   can  be  corrected  by  increasing  the  input  to  the  prime  mover.

2 answers
305 views
In dc machines, the armature windings are placed on the rotor because of the necessity for

Description : In dc machines, the armature windings are placed on the rotor because of the necessity for  (1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque

Last Answer : 3  Commutation

2 answers
134 views
Identify the increasing order of voltage regulation of the following dc generators a same load :

Description : Identify the increasing order of voltage regulation of the following dc generators a same load :  (A) differential compound, shunt and under compound  (B) shunt, differential compound and ... C) under compound, shunt and differential compound  (D) shunt, under compound and differential compound

Last Answer : Identify the increasing order of voltage regulation of the following dc generators a same load : under compound, shunt and differential compound 

1 answer
123 views
In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at

Description : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

Last Answer : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075

1 answer
134 views
In a DC generator the windings of interpoles are connected :

Description : In a DC generator the windings of interpoles are connected :  (A) in series with main field winding, to create a pole,of same polarity as the main pole ahead in the direction of rotation.  ... winding, to create a pole of opposite polarity as the main pole ahead in the direction of rotation.

Last Answer : In a DC generator the windings of interpoles are connected :  in series with the armature winding, to create a pole of same polarity as the main pole ahead in the direction of rotation. 

1 answer
2.5k views
The function of a brush and commutator arrangement in a dc motor is to

Description : The function of a brush and commutator arrangement in a dc motor is to  (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking

Last Answer : The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

1 answer
319 views
What is the difference between an AC and DC generator?

Description : What is the difference between an AC and DC generator?

Last Answer : The generator which generates DC voltage is called DC generator and generator which generates AC voltage is called AC generator (or) Alternator. In DC generator armature is rotated and field winding ... generator. A DC generator can generate low voltages but an AC generator can generate upto 11kv.

1 answer
69 views
What is the RPM of a DC motor?

Description : What is the RPM of a DC motor?

0 answers
81 views
What is the principle of DC generator?

Description : What is the principle of DC generator?

Last Answer : principle

1 answer
178 views
Why is the armature of DC generator laminated?

Description : Why is the armature of DC generator laminated?

Last Answer : The armature of DC generator is laminated to reduce eddy current losses.

1 answer
273 views
What are the speed control methods of dc motor?

Description : What are the speed control methods of dc motor?

Last Answer : Field control of DC motor Armature control of DC motor

2 answers
102 views
is induction motor ac or dc?

Last Answer : Induction motor is a AC motor it is also known as asynchronous motor .

1 answer
...